Re: [Qemu-devel] [PATCH] windows build: -lssp added to qga-vss.dll libraries list

[Stefan Weil]

Am 12.03.2015 um 15:08 schrieb Paolo Bonzini:
> On 11/03/2015 20:59, Stefan Weil wrote:
> > Am 11.03.2015 um 18:10 schrieb Joseph Hindin:
> > > When building qga-bss.dll with 64-bit mingw toolchain v. 4.9.2, the
> > Typo: qga-vss.dll
> >
> > > qga-vss.dll linking fails with unresolved symbols from libssp,
> > > stack protection support, like the following message:
> > >
> > > .../qga/vss-win32/install.cpp:52: undefined reference to
> > > `__stack_chk_fail'
> > >
> > > The patch fixes the problem by adding libssp to the qga-vss.dll
> > > libraries list.
> > >
> > > Signed-off-by: Joseph Hindin <address@hidden>
> > > ---
> > >    qga/vss-win32/Makefile.objs | 2 +-
> > >    1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/qga/vss-win32/Makefile.objs b/qga/vss-win32/Makefile.objs
> > > index 6a69d50..bd0840d 100644
> > > --- a/qga/vss-win32/Makefile.objs
> > > +++ b/qga/vss-win32/Makefile.objs
> > > @@ -5,7 +5,7 @@ qga-vss-dll-obj-y += requester.o provider.o install.o
> > >    obj-qga-vss-dll-obj-y = $(addprefix $(obj)/, $(qga-vss-dll-obj-y))
> > >    $(obj-qga-vss-dll-obj-y): QEMU_CXXFLAGS = $(filter-out
> > > -Wstrict-prototypes -Wmissing-prototypes -Wnested-externs
> > > -Wold-style-declaration -Wold-style-definition -Wredundant-decls
> > > -fstack-protector-all, $(QEMU_CFLAGS)) -Wno-unknown-pragmas
> > > -Wno-delete-non-virtual-dtor
> > >    -$(obj)/qga-vss.dll: LDFLAGS = -shared
> > > -Wl,--add-stdcall-alias,--enable-stdcall-fixup -lole32 -loleaut32
> > > -lshlwapi -luuid -static
> > > +$(obj)/qga-vss.dll: LDFLAGS = -shared
> > > -Wl,--add-stdcall-alias,--enable-stdcall-fixup -lole32 -loleaut32
> > > -lshlwapi -luuid -lssp -static
> > >    $(obj)/qga-vss.dll: $(obj-qga-vss-dll-obj-y)
> > > $(SRC_PATH)/$(obj)/qga-vss.def
> > >        $(call quiet-command,$(CXX) -o $@ $(qga-vss-dll-obj-y)
> > > $(SRC_PATH)/qga/vss-win32/qga-vss.def $(CXXFLAGS) $(LDFLAGS),"  LINK
> > > $(TARGET_DIR)$@")
> > >    
> > Adding -lssp works, but adding -fstack-protector-all to the linker flags
> > also works and might be the better solution.
> >
> > -$(obj)/qga-vss.dll: LDFLAGS = -shared
> > -Wl,--add-stdcall-alias,--enable-stdcall-fixup -lole32 -loleaut32
> > -lshlwapi -luuid -static
> > +$(obj)/qga-vss.dll: LDFLAGS = -fstack-protector-all -shared
> > -Wl,--add-stdcall-alias,--enable-stdcall-fixup -lole32 -loleaut32
> > -lshlwapi -luuid -static
> >
> > Could you please try that and send an updated patch? Please cc it also
> > to qemu-trivial.
> Actually it's not trivial...
>
> There is already an attempt to avoid the stack protector in
> qga/vss-win32/Makefile.objs:
>
> $(obj-qga-vss-dll-obj-y): QEMU_CXXFLAGS = $(filter-out -Wstrict-prototypes \
>      -Wmissing-prototypes -Wnested-externs -Wold-style-declaration \
>      -Wold-style-definition -Wredundant-decls -fstack-protector-all, \
>      $(QEMU_CFLAGS)) -Wno-unknown-pragmas -Wno-delete-non-virtual-dtor
>
> Perhaps you're using -fstack-protector-strong, and so the above line
> should use "-fstack-protector%"?
>
> Instead, if using the stack protector is fine, -fstack-protector-all
> should not be filtered out in the above line.
>
> In that case, I agree with Stefan that using -f is cleaner than -lssp,
> but it's even cleaner to make the flags match (i.e. it's unclean to
> have -fstack-protector-strong in the CFLAGS and -fstack-protector-all
> in the LDFLAGS).  So I'd do something like this to get the right flag:
>
> diff --git a/configure b/configure
> index 7ba4bcb..0e84b22 100755
> --- a/configure
> +++ b/configure
> @@ -1510,6 +1510,7 @@ if test "$stack_protector" != "no"; then
>       # setups fail only on a .c->.o compile and some only at link time
>       if do_cc $QEMU_CFLAGS -Werror $flag -c -o $TMPO $TMPC &&
>          compile_prog "-Werror $flag" ""; then
> +      stack_protector=$flag
>         QEMU_CFLAGS="$QEMU_CFLAGS $flag"
>         LIBTOOLFLAGS="$LIBTOOLFLAGS -Wc,$flag"
>         sp_on=1
> @@ -5003,6 +5004,7 @@ echo "LDFLAGS_NOPIE=$LDFLAGS_NOPIE" >> $config_host_mak
>   echo "LIBTOOLFLAGS=$LIBTOOLFLAGS" >> $config_host_mak
>   echo "LIBS+=$LIBS" >> $config_host_mak
>   echo "LIBS_TOOLS+=$libs_tools" >> $config_host_mak
> +echo "STACK_PROTECTOR_FLAG=$stack_protector" >> $config_host_mak
>   echo "EXESUF=$EXESUF" >> $config_host_mak
>   echo "DSOSUF=$DSOSUF" >> $config_host_mak
>   echo "LDFLAGS_SHARED=$LDFLAGS_SHARED" >> $config_host_mak
>
>
> and then use it in qga/vss-win32/Makefile.objs.
>
> Thanks,
>
> Paolo

Indeed, it's not trivial. Builds for Windows obviously are never 
trivial. :-(

My previous experience was gained with a Debian Jessie hosted cross build.
Now I have cross built on my standard environment with Debian Wheezy,
and there these modifications were needed:

diff --git a/qga/vss-win32/Makefile.objs b/qga/vss-win32/Makefile.objs
index 6a69d50..c501738 100644
--- a/qga/vss-win32/Makefile.objs
+++ b/qga/vss-win32/Makefile.objs
@@ -3,7 +3,7 @@
 qga-vss-dll-obj-y += requester.o provider.o install.o

 obj-qga-vss-dll-obj-y = $(addprefix $(obj)/, $(qga-vss-dll-obj-y))
-$(obj-qga-vss-dll-obj-y): QEMU_CXXFLAGS = $(filter-out 
-Wstrict-prototypes -Wmissing-prototypes -Wnested-externs 
-Wold-style-declaration -Wold-style-definition -Wredundant-decls 
-fstack-protector-all, $(QEMU_CFLAGS)) -Wno-unknown-pragmas 
-Wno-delete-non-virtual-dtor
+$(obj-qga-vss-dll-obj-y): QEMU_CXXFLAGS = $(filter-out 
-Wno-override-init -Wstrict-prototypes -Wmissing-prototypes 
-Wnested-externs -Wold-style-declaration -Wold-style-definition 
-Wredundant-decls -fstack-protector-all, $(QEMU_CFLAGS)) 
-Wno-unknown-pragmas

 $(obj)/qga-vss.dll: LDFLAGS = -shared 
-Wl,--add-stdcall-alias,--enable-stdcall-fixup -lole32 -loleaut32 
-lshlwapi -luuid -static
 $(obj)/qga-vss.dll: $(obj-qga-vss-dll-obj-y) 
$(SRC_PATH)/$(obj)/qga-vss.def
diff --git a/rules.mak b/rules.mak
index 7738121..bad44ba 100644
--- a/rules.mak
+++ b/rules.mak
@@ -102,7 +102,11 @@ endif
 %.o: %.dtrace
     $(call quiet-command,dtrace -o $@ -G -s $<, "  GEN $(TARGET_DIR)$@")

+ifdef CONFIG_WIN32
+%$(DSOSUF): CFLAGS += -DBUILD_DSO
+else
 %$(DSOSUF): CFLAGS += -fPIC -DBUILD_DSO
+endif
 %$(DSOSUF): LDFLAGS += $(LDFLAGS_SHARED)
 %$(DSOSUF): %.mo
     $(call LINK,$^)

Nothing with stack protection, but some compiler flags had to be removed...

Stefan